Fluid bed coal gasification - Gulf Oil Corporation
As we've previously reported and commented, there exists in the technical literature, especially in the records of the United States Patent and Trademark Office, an immense body of demonstrated knowledge clearly establishing the fact that Coal, and just about any other Carbon-based substance, including all sorts of Carbon Dioxide-recycling organic or botanical materials, and even Carbon Dioxide itself, can be transformed into what is known as synthesis gas, more simply just "syngas", a blend of Carbon Monoxide and Hydrogen, which can then be transformed through a variety of well-known and, within the petroleum industry, widely-used catalytic reaction processes into both liquid and gaseous hydrocarbons,
That knowledge base concerning the catalytic transformation of Carbon Monoxide with Hydrogen, and even of Carbon Dioxide with Hydrogen, into various hydrocarbons, is, in fact, almost vast; but, such chemical transactions, as we've pointed out in many of our reports, is often "lumped" under the generic label of Fischer-Tropsch" synthesis, named after the German scientists who, as seen in our report of:
Fischer & Tropsch Awarded 1930 US CoalTL Patent | Research & Development; concerning: "United States Patent 1,746,464 - Process for the Production of Paraffin-Hydrocarbons; 1930; Franz Fischer and Hans Tropsch, Germany; It is generally known that the oxides of carbon can be converted into methane by catalytic reduction (see Sabatier, Die Katalyse in der organischen Chemie, Leipzig, 1914) ... . ... (we) now have found that, instead of methane, its homologues (and) higher homologues which are easily liquefiable (or) liquid ... are obtained;
puzzled it all out more than eight decades ago.
The petroleum industry has continued to refine and further develop the Fischer-Tropsch synthesis, and it's analogue and derivative processes, ever since; most often, in their publications, failing to acknowledge that the synthesis gas can itself be derived from any Carbon source, including and most especially, as Fischer and Tropsch themselves first made it, from Coal.
That suspicion-arousing fact is illustrated quite well in one of our previous reports:
West Virginia Coal Association | Gulf and Chevron Convert Coal to Diesel Fuel and Gasoline | Research & Development; wherein we record no fewer than ten United States Patents issued to Pittsburgh, PA's former Gulf Oil Corporation and to California's Chevron, into which Gulf disappeared early in this century, which, as in one example:
"United States Patent 4,413,064 - Synthesis Gas Conversion for Preparation of Diesel Fuel; 1983; Assignee: Gulf Research and Development Company, Pittsburgh; Abstract: A catalyst useful in the conversion of synthesis gas to diesel fuel ... . A process for the conversion of synthesis gas to a product high in straight chain paraffins in the diesel fuel boiling range. Background: The growing importance of alternative energy sources has brought a renewed interest in the Fischer-Tropsch synthesis as one of the more attractive direct and environmentally acceptable paths to high quality transportation fuels. The Fischer-Tropsch synthesis involves the production of hydrocarbons of the catalyzed reaction of CO and hydrogen. Commercial plants have operated in Germany, South Africa and other parts of the world";
clearly state that we can affect the "production of hydrocarbons" through "the catalyzed reaction of CO and hydrogen"; but in only one or two instances confess that, as excerpted from another US patent included in that report:
"The source of the CO and hydrogen ... can be obtained, for example, by the oxidation of coal."
As we've emphasized, Pittsburgh's Gulf Oil does, though, have a long history of developing and establishing technologies to enable the conversion of, specifically, Coal into hydrocarbons, as seen, for example, in:
West Virginia Coal Association | 1953 Gulf Oil CoalTL Patent | Research & Development; concerning: "United States Patent 2,654,695 - Process for Preparing Liquid Hydrocarbon Fuel from Coal; 1953; Gulf Research and Development Company; Pittsburgh, PA; Abstract: This invention involves an improved combination of steps for preparing liquid hydrocarbon fuels from coal".
And, in separate United States patents, Gulf Oil did define the ways in which the needed "CO and hydrogen" synthesis gas blend could be made from Coal, as we've reported, for instance, in:
West Virginia Coal Association | Pittsburgh's Gulf Oil Liquefies & Gasifies Coal | Research & Development; concerning: "United States Patent 4,159,236 - Combining Coal Liquefaction and Gasification; 1979; Gulf Oil Corporation, Pittsburgh; Abstract: The prior art has disclosed a combination coal liquefaction-gasification process wherein ... the gasification zone (produces) the exact hydrogen requirement of the (total) process.
The present invention provides ... improvement in the ... efficiency of the combination process. This invention relates to a process wherein coal liquefaction and ... gasification operations are combined synergistically to provide an elevated ... efficiency. The liquefaction process produces for sale a significant quantity of both liquid fuels and hydrocarbon gases".
So sophisticated did Gulf Oil's technology for indirectly converting Coal into hydrocarbons become, that they even devised ways in which Coal could be converted into the more desired synthesis gas blend of Carbon Monoxide and Hydrogen with no co-production of Carbon Dioxide, as we reported in:
West Virginia Coal Association | Gulf Oil Uses CO2 to Gasify Coal | Research & Development; concerning: United States Patent 3,971,636 - Condensate Scrubbing of Coal Gasifier Product; 1976; Inventor: Charles Matthews, PA; Assignee: Gulf Oil Corporation, Pittsburgh; Abstract: A process for gasifying coal to produce carbon monoxide and hydrogen in which a first stream of coal is burned without bed formation in a combustion zone in the presence of water under oxidation conditions to produce gases containing carbon dioxide and steam. A second stream of coal is maintained as a fluid bed in a separate gasifier zone by upflowing carbon dioxide and steam from the combustion zone while being gasified under reducing conditions to produce carbon monoxide and hydrogen. The water vapor in the gasifier product stream is condensed and the condensate is used to scrub char and pollutants from the same gasifier product stream to form a slurry which is utilized as fuel in the combustion zone. Water is consumed within the process by the chemical reaction: C + H2O = CO + H2, and is thereby converted to the desired gaseous product. A high degree of process heat economy is achieved by virtually complete gasification of the carbonaceous portion of the feed. In accordance with the present invention, coal is converted to carbon monoxide and hydrogen by a process which exhibits a minimum potential for polluting".
And, herein, we learn that the inventor of the non-polluting "United States Patent 3,971,636 - Condensate Scrubbing of Coal Gasifier Product" went on to further refine the technology of Coal gasification for Gulf Oil, in order to, in a closely similar process, even more efficiently produce a blend of Hydrogen and Carbon Monoxide synthesis gas, essentially free of Carbon Dioxide and suitable for catalytic chemical condensation into various hydrocarbons, from Coal.
As seen in excerpts from the initial link in this dispatch to:
"United States Patent 3,971,639 - Fluid Bed Coal Gasification
Date: July, 1976
Inventor: Charles W. Matthews, PA
Assignee: Gulf Oil Corporation, Pittsburgh
Abstract: A process and apparatus for gasifying coal to produce carbon monoxide and hydrogen in which a first stream of coal is burned without bed formation in a combustion zone in the presence of water under oxidation conditions to produce gases containing carbon dioxide and steam. A second stream of coal is maintained as a fluid bed in a separate gasifier zone by upflowing carbon dioxide and steam from the combustion zone while being gasified under reducing conditions to produce carbon monoxide and hydrogen. Char produced in the fluid bed is elutriated overhead and material in the fluid bed is prevented from direct entry into the combustion zone. The ratio of carbonaceous material to ash in the char removed overhead is lower than the average ratio of carbonaceous material to ash in the solids in the fluid bed.
Claims: This invention relates to a process for gasifying coal, coke, or other carbonaceous solids to produce a gaseous mixture which, after removal of carbon dioxide and hydrogen sulfide, is composed mainly of carbon monoxide and hydrogen. The gaseous product may be utilized as a moderate Btu-content fuel; as a reducing gas for metallurgical and chemical purposes; and as an intermediate for conversion to hydrogen for use in chemical processes, in petroleum refineries, in coal conversion plants for manufacture of coal liquids or high Btu-content gas.
In accordance with the present invention, coal is converted to carbon monoxide and hydrogen by a process which exhibits a minimum potential for polluting. Essentially no water effluent is produced. Water makeup for use within the process as steam for gasification or as wash water may include polluted, solids-containing water from other processes. As a result, process requirements for fresh water are greatly reduced, and conventional requirements for purification and discharge of process waste water are similarly reduced.
Ash, entering as part of the coal feed, is removed from the process in the oxidized form as solidified slag, suitable for landfill or for additional processing to recover valuable minerals. Noncombustible solids introduced in water makeup from other processes or in raw water are also removed as part of the oxidized, solidified slag. Essentially no ash or other solids is rejected to the atmosphere.
(Note, that, as seen in another closely-related Gulf Oil patent, issued concurrently with the above-cited "United States Patent 3,971,636 - Condensate Scrubbing of Coal Gasifier Product":
Pittsburgh Pollution-Free Coal Hydrogasification | Research & Development; concerning: "United States Patent 3,971,635 - Coal Gasifier Having An Elutriated Feed Stream; 1976; Inventor: Charles Matthews, PA; Assignee: Gulf Oil Corporation; Abstract: A process for gasifying coal to produce carbon monoxide and hydrogen in which a first stream of coal is burned without bed formation in a combustion zone in the presence of water under oxidation conditions to produce gases containing carbon dioxide and steam. A second stream of coal is maintained as a fluid bed in a separate gasifier zone by upflowing carbon dioxide and steam from the combustion zone while being gasified under reducing conditions to produce carbon monoxide and hydrogen. Feed coal for both streams is first passed through a crusher and the crushed coal is elutriated to remove coal fines, which are too small to be retained in the gasifier fluid bed, from coarse particulates. The elutriated fines are water scrubbed to form a slurry which comprises at least in part said first stream of coal entering the combustion zone, while the coarse particulates comprise said second stream of coal. In accordance with the present invention, coal is converted to carbon monoxide and hydrogen by a process which exhibits a minimum potential for polluting. Essentially no water effluent is produced. Water makeup for use within the process as steam for gasification or as wash water may include polluted, solids-containing water from other processes. Ash, entering as part of the coal feed, is removed from the process in the oxidized form as solidified slag, suitable for landfill or for additional processing to recover valuable minerals. ... Essentially no ash or other solids is rejected to the atmosphere";
using identical, or almost identical, words and phrasing, Gulf Oil emphasizes that no objectionable materials need be emitted to the environment from a Coal gasification process.
And, as we've documented, for one example, in:
Iowa Mines Metals from Coal Ash for the USDOE | Research & Development; concerning: "United States Patent 4,386,057 - Recovery of Iron Oxide from Coal Fly Ash; 1983; Inventors: Michael Dobbins and Marlyn Murtha, Ames, Iowa; Assignee: The United States of America; The U.S. Government has rights in this invention pursuant to Contract No. W-7405-ENG-82 between the U.S. Department of Energy and Ames Laboratory. Abstract: A high quality iron oxide concentrate, suitable as a feed for blast and electric reduction furnaces is recovered from pulverized coal fly ash"; and: "United States Patent 4,397,822 - Process for the Recovery of Alumina from Fly Ash; 1983; Inventor: Marlyn Murtha, Iowa; Government Interests: The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-82 between the U.S. Department of Energy and Ames Laboratory. Abstract: An improvement in the lime-sinter process for recovering alumina from pulverized coal fly ash is disclosed. The addition of from 2 to 10 weight percent carbon and sulfur to the fly ash-calcium carbonate mixture increase alumina recovery at lower sintering temperatures";
"valuable minerals" can, indeed, be recovered from Coal Ash, as Gulf indicates. But, instead of consigning the remaining "slag" to a "landfill", as Gulf further suggests, we submit, that, as seen in:
Exxon Converts Coal Conversion Residues to Cement | Research & Development; concerning: "United States Patent 4,260,421 - Cement Production from Coal Conversion Residues; 1981; Assignee: Exxon Research and Engineering Company; Abstract: Cement is produced by feeding residue solids containing carbonaceous material and ash constituents obtained from converting a carbonaceous feed material into liquids and/or gases into a cement-making zone and burning the carbon in the residue solids to supply at least a portion of the energy required to convert the solids into cement";.
we can utilize the "residue solids" of a Coal gasification process, such as that of our subject, "United States Patent 3,971,639 - Fluid Bed Coal Gasification", in other, more productive and profitable ways.)
Gaseous impurities, having a potential for pollution, which are generated within the process are treated within the process and converted into acceptable forms for sale or disposal, or the impurities are destroyed within the process. For example, sulfur compounds entering the process are converted to hydrogen sulfide directly, or to sulfur dioxide and then to hydrogen sulfide; the hydrogen sulfide is recovered by known processes; and the recovered hydrogen sulfide is converted to elemental sulfur for sale or storage by use of known processes.
(Concerning the above, see, for one example:
Florida Hydrogen and Sulfur from H2S | Research & Development; concerning: "United States Patent 6,572,829 - Photocatalytic Process for Decomposing Hydrogen Sulfide; 2003; Assignee: University of Central Florida; Abstract: System for separating hydrogen and sulfur from hydrogen sulfide (H2S) gas produced from oil and gas waste streams. The sulfide solution ... converted to elemental sulfur and complexed with excess sulfide ion to make polysulfide ion, while water is reduced to hydrogen. Hydrogen percolates out of the photoreactor, while the polysulfide solution is fed back to the scrubber where the system starts over. A system for recovering sulfur from hydrogen sulfide (H2S) waste streams".)
Nitrogen compounds entering the process are converted mainly into ammonia, or to nitrogen gas, or to nitrogen oxides and then to ammonia or nitrogen gas; the ammonia is recovered and purified by known processes for sale. Gas streams before venting are first water scrubbed within the process to remove all dust and particulate contaminants.
Any traces of oils and tars which may be formed within the process are treated at high temperature to cause thermal cracking and are thereupon converted to gaseous or solid materials which are further reacted to form the desired gas product. At the same time, the improvements of the present process enhance process economy, especially in water usage, in process heat utilization, and in reliability.
Most water is consumed within the process by the chemical reaction: C + H2O ➝ CO + H2, and is thereby converted to the desired gaseous product. Only small amounts of water are lost as moisture vapor contained in vented nonpolluting gas streams. Makeup process water does not need to be treated, and, in fact, solids-containing and polluted water from other processes may be used.
(Note that "polluted water from other processes may be used", since the high heat of the Coal gasification would likely break down any, especially, organic pollutants; and, inorganic pollutants would as well be chemically reduced and bound into the Coal Ash. Maybe this would be a good way to utilize outflow from an older sewage treatment plant that might not be as efficient and effective as we all might hope.)
A high degree of process heat economy is achieved by virtually complete gasification of the carbonaceous portion of the feed. All fines and dusts are recovered within the process and then burned within the process in oxygen to generate the heat needed for gasification and for process steam generation. Process steam is generated internally with no heat transfer surfaces interposed between the source of heat and the vaporizing water, thereby avoiding most of the inefficiencies which are associated with steam generation in conventional boilers.
High temperature sensible heat is supplied for coal gasification; intermediate level sensible heat and latent heat generates high pressure steam for use in other processes; low level sensible heat and latent heat is rejected to the atmosphere by air coolers; therefore, a minimum of water cooling is needed.
Some of the advantages of process water economy and process heat economy are achieved interdependently. Water is used at many locations throughout the process to scrub particulates from gas streams and to cool hot particulates. The resulting slurry contains substantially all the ash from the process plus associated combustible material and dissolved pollutants. After settling, clarified water is recycled for additional scrubbing and cooling duties; the thickened, concentrated slurry is pumped at a controlled rate to the combustion chamber of the process where the combustibles are burned with oxygen to supply process heat; the slurry water is vaporized and superheated for reaction with coal; and the ash is melted to form slag which is easily separated from the process. In this manner, essentially no combustible carbonaceous matter is withdrawn from the process as byproduct or waste, and the process can accept and usefully burn undesirable high-sulfur, high-ash combustibles which are byproducts or wastes from other processes, such as the high-sulfur, high-ash solid wastes of a solvent coal liquefaction process.
(Concerning such "solvent coal liquefaction process"es, there have been any number of them developed over the decades. See, for instance:
West Virginia Coal Association | USDOE Funds Pennsylvania Coal Liquefaction | Research & Development; concerning both: "United States Patent 4,376,032 - Coal Liquefaction Desulfurization Process; 1983; Assignee: International Coal Refining Company, (PA); Abstract: In a solvent refined coal liquefaction process, more effective desulfurization of the high boiling point components is effected ... . The Government of the United States of America has rights in this invention pursuant to Contract No. DE-AC05-780R03054 (as modified) awarded by the U.S. Department of Energy"; and: "United States Patent 4,510,040 - Coal Liquefaction Process; 1985; Assignee: International Coal Refining Company, (PA); Abstract: This invention relates to an improved process for the production of liquid carbonaceous fuels and solvents from carbonaceous solid fuels, especially coal. The claimed improved process includes the hydrocracking of the light SRC mixed with a suitable hydrocracker solvent. The recycle of the resulting hydrocracked product, after separation and distillation, is used to produce a solvent for the hydrocracking of the light solvent refined coal. The Government of the United States of America has rights in this invention pursuant to Contract No. DE-AC05-780R03054 (as modified), awarded by the U.S. Department of Energy. The present invention involves an improvement in the process wherein "Light SRC" is the favored product, the "Heavy SRC" being recycled almost to extinction. Such Light SRC is, in turn, hydrocracked on a fixed catalyst bed to yield commercially useful liquid fuels"; and:
West Virginia Coal Association | Exxon 1982 CoalTL Uses WVU CoalTL Hydrogen Donor Solvent | Research & Development: concerning: "United States Patent 4,345,989 - Catalytic Hydrogen-donor Liquefaction Process; 1982; Assignee: Exxon Research and Engineering Company; Abstract: Coal or a similar solid carbonaceous feed material is converted into lower molecular weight liquid hydrocarbons by contacting the feed material with a hydrogen-donor solvent Claims: A catalytic hydrogen-donor liquefaction process for converting a solid carbonaceous feed material into lower molecular weight liquid hydrocarbons which comprises contacting said feed material with a hydrogen-donor solvent ... and a hydrogen-containing gas in ... the presence of an added carbon-alkali metal catalyst comprising a carbon-alkali metal reaction product prepared by partially gasifying an intimate mixture of carbonaceous solids and an alkali metal constituent with steam in a reaction zone external to said liquefaction zone. A process ... including the additional steps of recovering a heavy liquefaction bottoms fraction ... from the effluent of said final liquefaction zone; adding an alkali metal compound to said bottoms fraction to form an intimate mixture of said bottoms and said alkali metal compound; pyrolyzing said intimate mixture of said bottoms and said alkali metal compound to produce coke; gasifying said coke in the presence of steam; and using said gasified coke in each liquefaction zone in said series of liquefaction zones as said carbon-alkali metal catalyst. In the embodiments of the invention described ..., a portion of the solid carbonaceous feed material will remain unconverted after passing through the liquefaction zone or zones and is normally further converted in order to utilize the remaining carbon and thereby provide further economies to the overall liquefaction process. The further conversion will normally be carried out by gasifying the liquefaction bottoms or by coking the liquefaction bottoms and subsequently gasifying the resultant coke".
The above Exxon process utilizes a "hydrogen donor solvent", which is, by accounts, much more effective at liquefying the raw Coal, but, conversion efficiencies even in such more advanced solvent refined Coal processes, as our study of the literature suggests, still leave behind a carbonaceous residue that may contain, roughly, 10%, or more, of the original Carbon content of the Coal. That residual Carbon can be further extracted and indirectly converted, as in the above process of Exxon's "United States Patent 4,345,989 - Catalytic Hydrogen-donor Liquefaction Process"; or, directed to and used in the process of our subject, "United States Patent 3,971,639 - Fluid Bed Coal Gasification", as suggested by Gulf Oil, simply as fuel to help drive, i.e., "provide process heat" for, another, separate, Coal conversion process.)
Another advantage of the present process is its flexibility in using a variety of conventional fuels, combustible wastes, and potential pollutants as a source of heat for gasification of coal. These combustible materials, may have high sulfur content, high ash content, high moisture content but still would be useable. Such fuels are injected into the combustion zone where oxidation occurs. Sulfur oxides and nitrogen oxides which may be formed initially are ultimately reduced to hydrogen sulfide and nitrogen gas or ammonia within the process for easy separation and conversion to acceptable forms. Ash is melted and the slag withdrawn from the process with coal ash slag. Associated moisture is vaporized, superheated, and is reacted with coal to form the desired gas product."
---------------------------
One final note: Should anyone be interested enough to examine the full document, as accessible via the initial link in this dispatch, you will discover that Gulf specifies that this process can be applied to, in addition to some Carbon-recycling wastes, only "non-agglomerating" Coals, such as lignite. Our eastern bituminous Coals are specifically excluded, which seems strange for a Coal conversion technology developed by a company headquartered in Pittsburgh, PA.
Without getting into the specifics of what that means, the issue of eastern Coal agglomeration during gasification in a "fluidized bed", as specified by Gulf, is one we have addressed previously, and will treat further in future reports.
It is an easily resolved issue that was dealt with long ago by the US Bureau of Mines, as can be learned, for one example, via:
http://digicoll.manoa.hawaii.
Why the full text of a US Government report of work on Coal gasification, performed by Bureau of Mine scientists at a Pennsylvania laboratory, is accessible only on the University of Hawaii's web site is beyond our understanding, but not our suspicions.
That issue aside, our eastern bituminous Coal can easily be made to work just fine, along with a selection of Carbon-recycling organic wastes, in the Pittsburgh-developed process of our subject herein, "United States Patent 3,971,639 - Fluid Bed Coal Gasification"; a process which converts Coal and other, Carbon-recycling, "carbonaceous solids (into) a gaseous mixture... of carbon monoxide and hydrogen (which) may be utilized ... in coal conversion plants for manufacture of coal liquids or high Btu-content gas".